Passenger vehicles on the market today have a power transmission in the powertrain to provide multiple ratios between the engine and the driving wheels. Manual transmissions are employed in these vehicles because they provide more efficient powertrain usage due to the reduction in the amount of parasitic losses in the transmission.
Planetary transmissions are considered because of the lower cost of the gearing relative to countershafts in the normal manual transmission. However, the overall cost of automatically shifting a planetary transmissions is higher due to the increased complexity of the control mechanisms and the need for a pressurized hydraulic control system. Therefore, it is considered wise to combine a planetary-type transmission with synchronizer-type clutches and brakes for controlling the gear ratios. However, when employing synchronizers as the torque-transmitting mechanisms in planetary transmissions it is necessary to engage two or more of the torque-transmitting mechanisms simultaneously in order to produce a usable drive ratio within the planetary gear arrangement.
As set out above in more conventional automatic transmissions, the torque-transmitting mechanisms are fluid-operated devices controlled by a plurality of valves and electronic controls, which permit selected actuation and deactuation. Manual transmissions, however, employ synchronizers, which are mechanical in nature and generally controlled by a shift rail, which is manipulated by the operator. With manual planetary transmissions, as set forth above, it is necessary to engage or disengage two synchronizers to establish a drive ratio through the planetary arrangement.
Mechanical shift control mechanisms that will perform such a function are shown in U.S. Ser. No. 10/443,451, filed May 22, 2003, and U.S. Ser. No. 10/666,148, filed Sep. 18, 2003, both in the name of Haka and assigned to the assignee of the present application.